Implantable cardiac devices are used to treat a patient's heart that does not function normally due to, for example, a genetic or acquired condition. A typical implantable cardiac device may perform one or more functions including sensing signals generated in the heart, pacing the heart to maintain regular contractions and providing defibrillation shocks to the heart. Various techniques have been used to implant a cardiac device and associated leads.
An endocardial implantation technique generally involves gaining access to the interior of the heart via the venous return and implanting several leads within the heart. For example, an implantable device including circuitry for sensing signals from and generating stimulation signals for the heart may be subcutaneously implanted in the pectoral region of the patient. Leads connected to the device are routed from the device through a vein to the right side of the heart. A distal end of the lead may then be passively or actively attached to an inner wall of the heart.
An epicardial implantation technique generally involves implanting leads at an outer layer of the heart (the epicardium). Historically, an implantable device including the sensing and pacing circuitry was implanted in the abdominal region of the patient. Sensing/stimulation leads were then run from the device to the epicardium.
Alternatively, the device also may be implanted in the pectoral region of the patient for an epicardial implantation technique. In this case, a tunnel is formed under the patient's skin between the implant site for the device and the heart. Leads are then routed via the tunnel from the device to the lead implant site in the epicardium.
There are several disadvantages that may be associated with the above implantation techniques. For example, placement of the implanted device in the abdomen may be relatively uncomfortable for the patient. In addition, defibrillation vectors that incorporate the implanted device as an electrode may be suboptimal. Conversely, creating a tunnel between the pectoral region and the heart may be traumatic for a patient and may require a relatively long recovery period.